US 3096833 A
Description (OCR text may contain errors)
July 9, 1963 A. e. BODINE some EARTH BORING DRILL WITH JACKET 5 Sheets-Sheet 1 Filed Feb.
6 m m m M 02 7535 lTjv 579 6 m iii; i 2&3; a i g i A Q z QR k Vw ZL/ /7 1% ,i 4 y E .1 B a 1 I w 47' 47 p k July 9, 1963 A. G. BODINE 3,096,833
some EARTH BORING DRILL WITH JACKET s Sheets-Sheet 2 Filed Feb. 1, 1960 United States Patent 3,096,833 SONIC EARTH BORING DRILL WITH JACKET Albert G. Bodine, Sherman Oaks, Calif. (3300 Cahuenga Blvd, Los Angeles 28, Calif.) Filed Feb. 1, 1960, Ser. No. 5,792 3 Claims. (Cl. 175-56) This invention relates generally to so-called sonic well drills, of the general class disclosed in my Patent No. 2,5 5 4,005, and more particularly to improvements in sonic drills operating at high energy levels.
As is well known, there is a current trend in oil well drilling practice toward the drilling of deeper but more slender bores, particularly in regions where the productive formation is very deep underground, and the formation to be penetrated includes unusually hard strata. The adaptation of the sonic drill to such conditions dictates higher energy operation generally, and favors also the use of higher sonic frequencies. Under such conditions, there are encountered certain new problems, or old problems of very much increased severity. That is to say, certain unfavorable behaviors of the sonic drill which could formerly either be overlooked, or dealt with adequately by previously known procedures, have now become so severe and troublesome as to require new remedies for their control. The general object of the present invention is to provide means for meeeting these problems.
A sonic drill such as disclosed in my said patent comprises, generally, an elastic column such as a section of heavy steel drill collar, typically from one to several hundred feet in length, suspended from :a conventional drill string, the collar being coupled at its lower end to a drill bit, and a longitudinal sonic standing wave being maintained in this collar by a suitable oscillator adapted to apply a periodic force to an end of the elastic column at a resonant frequency of the latter. The standing wave is a free-free pattern, such that velocity anti-nodes occur at both ends of the column, with one or more velocity nodes (stress anti-nodes) intervening therebetween. The standing wave pattern may be of half-wavelength, in which case velocity antinodes occur at both ends of the column, with a stress antinode at its midpoint, which is a quarter-wavelength distance from each end. Alternatively, the column can be driven at harmonic frequencies giving any multiple of a half-wavelength along the column. In any such case, the velocity antinodes occur at the two ends of the column and at half-wavelength distances therealong, with stress antinodes occurring midway between velocity antinodes. The velocity antinode condition at the lower end of the column is both essential and useful in that maximized vibration at this point is required in order to vibrate the bit against the formation. The velocity antinode at the upper end of the column, however, while an inherent characteristic of such a system, actually presents a considerable problem in that it affords a poor coupling point to the supporting drill string. Thus, the velocity antinode at the upper end of the column undesirably sends sonic waves up the supporting drill string when directly coupled thereto, causing a serious loss of sonic energy, and undesirable vibration of the drill string. Vibration isolators have been provided for intercoupling between the drill string and the vibratory upper end of the elastic column and have been found very useful under certain conditions, but introduce some 2 complication, and it would be an undoubted advantage if they could be avoided.
One object of the present invention is accordingly the provision of a suspension system for a sonic drill, particularly one of high energy and frequency, which avoids coupling to the velocity antinode region at the upper extremity of the elastic vibratory column, and which therefore meets the problem in question by avoiding it rather than contending with it as do the isolators.
Another problem inherent in sonic drills, particularly severe and troublesome when operated under high energy conditions and at increased frequencies, is an insistent proneness to substantial lateral vibration. While the periodic force impulses applied to the drill column are directly longitudinally, the slightest lateral unbalance in the equipment results in a parasitic lateral mode of vibration in the column. This appears as lateral Wave action coursing along the column. Since wave length for lateral waves is considerably shorter than for longitudinal waves, several wave lengths of lateral vibration can occur along the half-wavelength (for longitudinal vibration) column. The lateral waves can also occur, under some conditions, at resonant frequencies and lateral standing Waves can develop. Such lateral vibration, depending upon the design of the apparatus, and the power at which it is driven, can attain large amplitudes. Under extra hard driving, for example, the amplitude may reach a half inch; though under such conditions, the column would be overstressed and soon rupture. These conditions are very undesirable for a number of reasons. First, substantial lateral vibration consumes a corresponding degree of available sonic energy generated for driving the drill. Secondly, a lateral vibration applies a cyclic bending stress in the column, which greatly reduces the life of the column. There are additional problems attendant upon lateral vibrations, such as improper bit action, damage to the side walls of the Well, undesirable side lo ads in the oscillator mechanism, etc.
It is accordingly an important and primary object of the invention to provide means for suppressing parasitic lateral vibration of the longitudinally vibratory drill column.
The present invention, in the aspect of suppression of lateral vibration, stems from the discovery of a very surprising wave damping efiect provided by the use of a slight lateral, or annular, clearance between the longitudinally vibratory resonating bar and a surrounding jacket structure which extends lengthwise of the bar for a substantial portion of a quarter-wavelength (longitudinal) distance along the bar. The lateral clearance gap is made sufficiently small, typically, for example, one-eighth inch, so as to assure that lateral vibration of the bar will result in elastic collision between the bar and jacket structure, and bounce-bac of the bar. The bar is thus prevented from following the parasitic lateral wave, and building up a large amplitude lateral wave action. Instead, it is thrown sharply back, out of phase with the parasitic lateral wave, and its initial or incipient lateral vibratory action breaks up into a large number of non-linear low amplitude and highly damped components of various frequencies and phase relations. The mathematics of such non-linear eifects is highly abstruse, and the damping eifect discovered was essentially unpredictable. Sutfice it to say that critical damping of the bar against lateral vibration is attained, i.e., the energy of the incipient lateral parasitic wave is absorbed and dissipated as fast as supplied, and the parasitic lateral wave is prevented from developing. In fact, the throwing of the bar out of phase with the incipient lateral wave not only prevents development of the lateral wave, but conserves energy that would otherwise be diverted into the lateral wave. Thus only a fraction of the energy otherwise diverted into the parasitic lateral Wave is converted into lateral wave action, and this energy fraction is dissipated or critically damped by rapidly decaying non-linear low amplitude lateral vibration components of various phase relations and frequencies.
The lateral wave damping phenomenon here described differs from what occurs with other jacket structures used in prior sonic drills. For example, in FIG. 24 of my aforementioned Patent No. 2,554,005 is shown a jacket 573 surrounding a longitudinally vibratory bar or column 560, but in which the clearance space between column and jacket was described as sufficiently ample to accommodate maximum elastic deformation of the column without making contact with the sides of the jacket. It would of course be understood that this implies a normal, nondestructive degree of drive effort for the apparatus. Similarly, certain structural configurations in my Patent No. 2,903,242 show annularly spaced members, one of which is longitudinally vibratory; but in these cases, as scaling of the drawings will reveal, the annular clearance gap is of a substantially 'wider order than is here contemplated, or than would permit lateral collision between the members under any normal or non-destructive degree of drive effort.
An illustrative embodiment of the invention, accomplishing both the objective of suspension of the longitudinally vibratory column at a point other than its vibratory upper end, and the objective of surrounding a substantial longitudinal extent of the column with a close fitting but slightly spaced jacket, may be described briefly as follows: The elastic vibratory column member is provided with an elongated jacket structure extending downwardly thereover at slight spacing therefrom, to the region of a stress antinode in the column member, at which point the jacket is rigidly connected thereto. The upper end of the jacket structure is connected to the supporting drill string, and the bit is coupled to the lower end of the elastic column. A periodic force generating oscillator is coupled to the column at one or more antinodes of the longitudinal wave therein. The coupling may be to the upper end of the elastic column, in which case the oscillator may be housed within the upper end of the aforementioned jacket structure. Alternatively, the oscillator may be intercoupled between the lower end of the elastic column and the bit. Moreover, it is sometimes desirable to have two oscillators, one at each end. The vibratory column is thus suspended from the drill string through the jacket at a stress antinode point (region of no vibration), so that no vibration energy leaks up the drill string. And the same jacket structure accomplishes critical damping of lateral vibration.
A still further object of the invention is the provision of a simple hydraulically actuated oscillator for generating and applying the periodic force impulses against the elastic column, characterized by mechanical simplicity, ruggedness, and capability of generating periodic force impulses at high energy levels. A feature of this oscillator is that its periodic force is generated along a vertical direction line, without lateral force components requiring balancing, and which therefore is not a source of lateral vibration. In this connection, the common mechanical oscillator involving a number of unbalanced rotors are of course ordinarily designed for cancellation of lateral force components. However, it is extremely difiicult to attain perfect cancellation, and also to avoid force couples, and a tendency for lateral wave generation has remained as a problem with this prior oscillator.
The details and accomplishments of the hydraulic oscillator may best be described in the body of the specification.
Reference is now directed to the accompanying drawings, showing certain present illustrative embodiments of the invention, and wherein:
FIG. 1 is a view partly in elevation and partly in longitudinal section showing an embodiment of drilling system in accordance with the invention;
FIG. 2 is a section taken in accordance with line 2-2 of FIG. 1;
FIG. 3 is a section taken in accordance with line 33 of HG. 2;
FIG. 4 is a detail section taken on line 44 of FIG. 3;
FIG. 5 is another detail taken on line 55 of FIG. 3;
FIG. 6 is a section taken on line 66 of FIG. 2;
FIG. 7 is a view similar to FIG. 1 but showing a modified form of the invention; and
FIG. 8 is another view similar to FIG. 1 but showing another modified form of the invention.
Reference is first directed to the illustrative embodiment of the invention shown in FIGS. 1 to 6. Numeral 10 designates generally the lower extremity of a conventional drill string, understood to extend downwardly in the well from the ground surface, and formed at its lower end with a box coupling 11 which receives the threaded pin 12 on the upper end of the upper tubular member 13 of a jacket structure generally indicated by the numeral 14. Jacket structure 14- comprises, in addition to upper tubular member 13, a long inter-mediate sleeve 15 screw-coupled, as [at 16, to the lower end of member 13, and also a lower tubular coupling member 17, screw-coupled as at 18, to the lower end of sleeve 15, and firmly joined, as at 19, to a mid-portion of longitudinally vibratory elastic drill column 20. This column 20 is composed preferably of a good grade of alloy steel. In the particular embodiment here shown, the column 20 comprises an upper section 21, of a typical diameter of 5 inches, and a lower section 22 of somewhat larger diameter, typically 6 inches, joined by a short tapered intermediate portion 23 to which the coupling member 17 is secured. As here shown, the lower end of coupling member 17 has an internal taper complementary to the taper of column portion 23, and is joined to the latter by a press fit. Thus the upper section 21 of column 21) extends upwardly through jacket 14, and to the upper end thereof is coupled a periodic force generating oscillator 24 which is housed within the upper end portion of the jacket, as shown.
A usual bit 25 is coupled to the lower end of column 20, and for the size of column heretofore mentioned, may have a bit circle diameter of 7%". This bit circle is of slightly larger diameter than jacket 14, so as to provide clearance for the jacket in the bore hole. This clearance is preferably made slight, so that the jacket will have a comparatively close fit in the well bore, and will therefore be laterally guided and supported thereby against substantial lateral jacket vibration.
As disclosed in my aforesaid Patent No. 2,554,005, the oscillator 24, details of a present illustrative embodiment of which will be described hereinafter, applies a vertically oriented periodic alternating force to the upper end of \colunm 20 at a resonant frequency thereof for half-wavelength standing wave vibration, or a multiple thereof, resulting in periodic alternate elastic elongation and contraction of the column. The midpoint, at region 23, stands virtually stationary, and is a location of a velocity node of the standing wave set up in the column. Opposite end portions of the column vibrate vertically in opposite directions as the two half portions of the bar simultaneously undergo alternate elastic elongation and contraction, and these opposite end portions of the column are the locations of velocity antinodes of the standing wave. In view of the somewhat smaller outside diameter of the upper portion of the bar as compared with the lower portion thereof, the velocity node actually appears at a point spaced somewhat downwardly from the exact longitudinal midpoint of the column. Taking into account the mass and geometry of the oscillator 24 connected to the upper end section of the bar and of the bit 25 connected to the lower section thereof, the velocity node is located at the center of mass of the vibratory system; and coupling member 17 is preferably joined to the column at that point.
It is, however, not critical that the jacket be joined to the column 20 at the exact center of mass, i.e., at the exact velocity node, and it is sufiicient for ordinary practical purposes, from the standpoint of suspension, that the jacket be joined to the column somewhere along its midregion, but not too close to its ends. Of course, the farther the point of column suspension from its upper end, the less will be the vibration transmitted into the suspension. The most important consideration is that the point of column suspension be well down from its upper end antinodal region, where vibration is at a maximum. To particularize somewhat more definitely, benefits of the suspension in accordance with the invention are substantial when the coupling point of the suspending jacket to the column is of the order of an eighth wave-length or more down from the upper extremity thereof. In this connection, the jacket structure is relatively thin walled and complaint, and quite capable of absorbing a consider-': able degree of vibration, such as that encountered at the eighth Wave-length point. Ideally, of course, and to secure the maximum benefit of the invention, the jacket should join the column at substantially the velocity nodal point, where column vibration is virtually nil.
The illustrative embodiment of the invention was designed for half wave-length operation at resonant frequency of 185 cycles per second. At this frequency, the vertical dimension of the apparatus from the top of jacket coupling pin 12 to the bottom bit 25 is approximately 45 feet. In this connection, and when considering the drawings, it may be assumed that equal lengths of column have been removed at the two breaks above and below the midpoint of the column.
The housing of the oscillator 24 is cylindrical, and, as shown in FIG. 1, of the same outside diameter as the upper column section 21. The side Walls of the tubular jacket sections, excepting at their intercoupling regions, are annularly spaced by a very small clearance distance x, of the typical order of from the outside surface of the upper column section 21 and oscillator housing. At the coupling between jacket sections 15 and 17, the jacket wall section is increased to accommodate the coupling; and here the clearance distance is reduced still further, but a slight play is still preferably provided. Similarly, a reduction in clearance is shown at the coupling between jacket sections 13 and 15. In the alternative, jacket sections 13 and 15 may be integral with one another, and the coupling 16 omitted, so that no reduction in clearance distance occurs at that point.
The clearance distance x is made in all cases substantially less than the normal amplitude of lateral vibration to be anticipated under normal running conditions, so that the column, in expected normal operation, tends to vibrate laterally at a greater amplitude than the provided clearance distance, and therefore strikes sharply against the side wall of the jacket. The reduced clearances at the coupling points in the jacket do not prevent this desired striking action, since the lateral vibration travels in Waves along the column, and even if the column is closely confined at the jacket coupling points, these waves of lateral vibration develop an amplitude a relative short distance beyond the coupling points that is suflicient to assure collision of the column with the jacket. The benefit resulting from such lateral collision was described preliminarily, and will be further mentioned hereinafter.
With reference now to FIGS. 26, a hydraulic oscillator in accordance with the invention will now be described.
The upper end of upper column section 21 is formed with a screw-threaded box 30 and into this box is screwed the threaded coupling pin 31 on the lower end of the body 32 of the periodic force generator 33 of oscillator unit 24. Body 32 has, immediately above pin 31, an exterior annular flange 35 seating on the shoulder at the upper end of column 21, and has, above flange 35, a threaded portion 36 to which is threadedly joined the lower extremity of the tubular side wall 37 of the oscillator housing. An annular clearance 38 is provided between body 32 and wall 37 for flow of operating fluid (mud fluid such as is used in rotary drilling of wells), while above body 32, the wall 37 has a thickened section such as indicated at 37a. Housed inside the thickened wall section 37a is the driver for the periodic force generator 33, comprising in this case a turbine 40 driven by mud fluid circulated through the apparatus.
In operation, mud fluid is circulated downwardly through drill pipe string 10, and flows into the upper end of jacket structure 14 by way of port 41 formed in coupling pin 12 and opening into the top end of the jacket as shown in FIG. 1. Mounted in the upper end portion of the bore 42 defined by housing wall portion 37a is a short tube or sleeve 43 formed with spokes or webs 44 supporting an inverted cup 45 which directs mud fluid received from above into an annular flow stream between the sleeve 43 and the sidewall of the cup. A turbine stator 46 comprising a sleeve 47 seated in bore 42 below sleeve 43 carries a plurality of vertically spaced sets of angularly disposed turbine stator vanes 48 of conventional nature which, as will be seen from the drawings, are in line with the annular mud fluid flow stream directed downwardly between sleeve 43 and inverted cup 45.
Intervening between the stator vanes 48 are a plurality of vertically spaced sets of angularly disposed turbine rotor vanes 49, carried by a rotor sleeve 50 having a transverse Wall 51 and a hub 52 mounted on a central rotor shaft 53. The rotor shaft is journalled in a bushing 54 seated in a tubular stem 55 projecting upwardly from a head 56 screwed into the top end of generator body 32, and received within rotor sleeve 50 below wall 51. A cap 57 on the upper end of stem 55 confines packing 58 for shaft 53 against mud fluid present in the space between said stem and the turbine rotor.
Body 32 has extending downwardly into its upper end a bore 60 formed with threads at its upper end for reception of head 56. Bore 60 terminates at a shoulder 62; and below shoulder 62, bore 60 is continued by a smaller diameter bore 63 having a bottom 64. Rising from bottom 64, at annularspacing inside bore 63, is a tubular Wall 65 whose upper end terminates at the level of shoulder 62. Aperture 66 in wall 65 near bottom 64 establish fluid communication between the lower end portion of the bore 67 of wall 65 and the lower end portion of the annular space 68 between Wall 65 and the wall surface defining the bore 63. An annular, vertically oscillatory inertia mass or piston 69 is positioned with a free sliding fit in annular space 68.
Turbine rotor shaft 53 has on its lower end a cylindrical pump rotor 70, the upward surface of which is immediately below head 56, and the lower surface of which rests on a disk 71 seated tightly in the bottonr of bore 64 on shoulder 62.
Rotor 70 turns within an elliptical chamber 74 formed within a rang 75 seated on disk 71 and fitted tightly in the bore 69 in the wall of body member 33. As shown in FIG. 3, the rotor '70 has a close turning fit with the wall surface of the elliptical chamber 74 in the plane of the minor axis of the ellipse, while there is a substantial clearance space between the rotor and the wall surface of the elliptical chamber in the plane of the major axis of the ellipse. Two crescent-shaped spaces 76 are thus formed between the rotor and the wall surface of the elliptical chamber 74.
The rotor is formed with four vertical slots 78 in radial planes spaced degrees apart, and radially slidable in these slots are vanes 79, whose rounded outer edges bear on the wall surface of the elliptical chamber. The outer edges of the vanes bear constantly on the wall surface of the elliptical chamber during rotor rotation by virtue of centrifugal force. They thus alternately extend and recede in travelling around the elliptical chamber.
The rotor is formed in two opposite quadrants defined by the four vanes 79 with a pair of vertical throughpassages 86 at radii such as to align with annular piston chamber 68 and in the remaining quadrants with a pair of through-passages 81 at radii such as to align with the bore 67 in tubular walls 65. These passages are ported radially outward through the side wall of the upper portion of the rotor, as at 82 for passages 80, and as at 83 for passages 81, so as to be communicable with the crescent shaped spaces 76.
The disk 71 is provided with a circular series of ports 84- at a radius equal to that of rotor ports 80, and with another circular series of ports 85 at a radius equal to that of rotor ports 81. The ports 84, and also the ports 85, are spaced by thin webs, as shown in FIG. 6. These ports establish fluid communication between passages 80 and chamber 68 above piston 69, and between passages 81 and bore 67, in all positions of the rotor.
The various described ports and passages, including the crescent shaped spaces 76, the chamber 68 above and below piston 69, and the bore 67, are filled with a suitable hydraulic fluid, preferably a light oil. It will be understood that mud fluid is circulated down drill pipe string 10, at a pressure and flow rate controlled by a usual surface pump, not shown. It will further be understood that such surface pump is driven by a suitable prime mover, such as a controllable internal combustion engine. Thus mud fluid flows downwardly through the annular channel occupied by the turbine stator and rotor blades, imparting rotation to the turbine rotor, and to shaft 53 and pump rotor 70. Below the turbine blades, the mud fluid discharges via a short outwardly extending passageway 86 between head 56 and the lower end of the thickened portion 37a of wall 37 to the previously described annular duct 38. Below the lower end of the bore 63, the mud fluid in duct 38 flows inwardly into body 32 via ports 89 to a circulation bore 88 extending through the lower end of body 32 and through the entire length of column 20 to the bit, through which it then passes and finally discharges therefrom by way of ports 89 in a conventional manner.
Pump rotor 70 is thus rotated by the mud fluid driven turbine. As it does so, as previously explained, its blades or names 79 sweep around the elliptical chamber 74, oscillating in and out, to follow the contour of the chamber. These vanes, forced outwardly by centrifugal force, bear forceably against the elliptical wall surface of the chamber, sealing thereagainst, and providing four separate compartments, 0, b, c, and d, of variable displacement, between the rotor and the wall surface of the elliptical chamber 74.
In the rotor position shown in FIG. 3, diametrically opposite compartments a and c, which are in constant communication via passages 81 with the bore 67 below and are therefore in communication via ports 66 with the space in annular chamber 68 below the oscillatory piston 69, are at this time at maximum displacement volume. At the same time, compartments b and d, which are in constant communication via passages 80 with the space in chamber 68 above piston 69, are at minimum displacement volume. In this position of the pump, the piston 69 is evidently at its lowermost stroke position in chamber 68, as shown in FIG. 2.
Now, as rotor 70 turns to the right, for example, through a quarter turn distance, the compartments a and c are reduced from maximum to minimum volume, and fluid is forced downwardly through passages 81 into bore 67 and thence through ports 66 to the space in chamber 68 below piston 69 to drive the latter upwardly. At the .same time, the compartments b and d are increased from minimum to maximum volume, and fluid above the piston in chamber 68 accordingly flows upward through rotor passages to fill the increasing volume of these compartments. The annular piston member 69 is thus permitted to rise by evacuation of the fluid from above it, as to the position shown in FIG. 2 in phantom lines. Of course, during the next quarter turn of the rotor, fluid flows in the reverse direction, so that the piston 69 then returns to its originally assumed lowermost position.
The piston 69 thus rises and falls, completing one full cycle during each half turn of rotor 70. Two cycles of piston oscillation are thus generated per rotor revolution.
The piston 69 acts as an inertia device, exerting a vertical alternating reaction force on body member 32 through the liquid bodies in the chamber 68 above and below the piston. Body 32 accordingly is subjected to a periodic alternating vertically oriented force; and it will be seen that this periodic alternating force is exerted on the upper end of the elastic column 20 to which the body 32 is coupled. It will further be noted that this alternating force is generated without lateral components of force.
The mud fluid is circulated by the ground surface pump to rotate the turbine at a speed which will cause alternating force generation at a frequency approximating the resonant frequency of the elastic column 20 for a mode of longitudinal resonant standing wave vibration thereof. As stated, this is in the region, for the illustrative embodiment here described, of cycles per second. The attainment of this frequency is readily recogniza-ble at the ground surface. The apparatus settles down to steady drilling, and those familiar with this type of apparatus can immediately recognize resonant performance by characteristic noise manifestation, and by a tendency for the prime mover driving the pump to lock in at a steady speed. If necessary, a vibration pick-up device coupled to the drill pipe string at the ground surface will indicate, merely by the amplitude of its response, that performance is at resonant frequency.
At such time, the column vibrates in the characteristic longitudinal half-wave manner, and drilling proceeds.
As parasitic lateral waves tend to occur in the elastic column, the column deflects laterally, and when the half amplitude of such lateral wave action tends to exceed the dimension of the very small clearance space x between the column and the jacket structure, the column collides elastically with the jacket, and bounces back. Thus the lateral wave is broken up, the column moving in an out-of-phase relation -to the incipient lateral wave tending to be started. The nature of the critical damping of the lateral vibration wave in the column by such enforced collision of the column with the jacket structure was described as fully as now understood in the introductory part of this specification, and need not here be repeated. Suffice it to say here that the phenomena was discovered to be surprisingly effective in suppressing the lateral wave.
It will also :be clear that the jacket structure, coupled to the vibratory column 20 in the region of a node of the column, furnishes an ideal solution to the problem of vibration transmission from the column to the drill string. If the jacket is coupled to the column precisely at the node of the longitudinal wave, vibration transmission up the drill string is virtually nil. In practice, as heretofore noted, it is not essential that the coupling point be precisely at a node, and a certain range of lee- Way is permissible, as previously described.
It may here be mentioned that, while half-wave standing wave operation, as described above, is the normal or most obvious longitudinal standing wave mode, broadly speaking, the operation can be at any multiple of halfwavelengths, such as full wavelengths, one and one-half wavelengths, etc, by driving the oscillator at appropriate harmonic frequencies.
In FIG. 7 I have shown a modified arrangement of drill in accordance with the invention wherein the oscillator 24a is inter-coupled between the lower end of the longitudinally vibratory elastic column 20a and the hit 2511. The apparatus is again suspended from the lower end of drill pipe string a through close-fitting jacket structure 14a secured to the column 20:: in the region of a velocity node of the latter, as at 19a. The upper section 21a of the column extends well up within the jacket structure, which in this instance is in one piece down to the lower tubular coupling member 17a Where attachment is made to the column, and the annular clearance space between column section 21a and the jacket structure 12a is again very small, typically of the order of A3 inch, or in other words, of substantially less dimension than the normal half-amplitude of lateral vibration.
The oscillator 24a may be of any type adapted to apply a periodic alternating force to the lower end of the oscillatory column at the resonant frequency of the latter, but may, if desired, be of the general type shown in FIGS. 2 to 6, with slight modification to adapt it to its new situation. For example, the upper end portion of the oscillator housing may be furnished with a threaded coupling pin 90 screwed into a corresponding box in the lower end of column 20a, and the circulation passage 91 through the column may deliver mud fluid through the coupling box 90 to a turbine and vane pump driving a vertically oscillating inertia system as shown in FIGS. 2 and 6. Fluid exhausted from the turbine will be understood to pass downwardly in the same manner as shown in FIG. 2 for delivery to and discharge from the bit, all as will be clearly understood. The embodiment of FIG. 7 operates exactly as does that previously described, with the sole exception that the periodic force application to the column 20a is at the lower end of the latter rather than at the upper end thereof. It will further be understood that an oscillator may be used at the upper end of column 20a, as in FIG. 1, and another oscillator may be used at the lower end thereof, as in FIG. 7. Longitudinal standing wave vibration of the column 20a automatically synchronizes the operation of the two oscillators so that the inertia pistons thereof oscillate vertically in unison. This phenomenon is owing to a back reaction exerted by the driven longitudinally vibratory column 20a on the oscillatory pistons, tending to cause them to lock in in synchronism with one another at the resonant longitudinal standing wave frequency of the column. I have discovered that this can be accomplished if the turbine torque is much less than the critical value of resonance breakover.
In FIG. 8, I have shown another embodiment of the invention, utilizing in this case an oscillator driven by an electric motor, and without fluid circulation through the apparatus. It will of course be understood in this connection that the drill of FIG. 8 is intended for applications wherein flu-id circulation upwardly around the drilling apparatus during drilling is not required.
The housing of a vertically oriented electric drive motor 99 is indicated at 100 at the top end of the sonic drill, and while this motor housing may be suspended from a usual drill pipe string, it may also, in this case, be lowered on a cable or wire line. To this end, the motor housing is shown furnished at its top end with an eye 101 for coupling to a wire line, not shown. Electric power for operation of motor 100 is conveyed thereto by way of electric cable 102. The lower end of motor housing 100 is screw-coupled, as at 103, to the upper sleeve 104 of a three part jacket structure generally designated at 105, and which comprises, in addition to sleeve 104, a long intermediate sleeve 106 screw coupled to sleeve 104 as at 107 and a lower coupling sleeve 108 screw coupled as at 109 to intermediate sleeve 106, and made fast, as at 109, in the manner of the embodiment of FIG. 1, to the mid-portion 110 of longitudinally vibratory elastic column 111. As in earlier embodiments this column 111 includes an upper section 112 at small clearance distance from jacket structure 105, so as to be struck by the column when vibrating laterally, nad a lower section 113, of slightly enlarged diameter, carrying at its lower end a bit 114. The periodic alternating force generator 115 is secured to the upper end of column 111.
The housing of the electric drive motor will be seen to be secured to, or to be, in eitect, a part of the jacket structure 105. The motor has a vertical, downwardly extending shaft 116 formed with an internally splined bore 117 which receives an externally splined shaft 118 for the fragmentarily indicated rotor 119 of a vane pump such as that more particularly illustrated in FIGS. 2-6, and which will be understood to effect vertical reciprocation of an inertia piston through hydraulic means as in the oscillator of FIGS. 2-6. These parts are contained within the cylindrical housing of periodic force generator 115, and which is screw-coupled, as at 120, to the upper end of column 111.
Operation of the drill is essentially the same as that of the embodiments first described, with the exception of the fact that the driver of the oscillator, in this case an electric drive motor, is mounted to the upper end of the jacket structure, where longitudinal vibration is absent, while the force generator of the oscillator is coupled to the longitudinally vibratory upper end of the column; and the splined shaft coupling between the motor shaft of the driver and the rotor of the force generator accommodates the relative longitudinal motion between the driver and force generator. It is of course an obvious advantage to have the driver in a non-vibrating situation.
I have found that a very important advantage is attainable if the force generating oscillators of the several disclosed forms of the invention are driven with an eifort just less than that for peak longitudinal resonance in the column, or just under that critical value which will cause breakover above the desired longitudinal resonance frequency of the column. The system is them stabilized in a desirable form of longitudinal resonant performance, with lateral vibration suppressed, as described.
It will be understood that the drawings and description of the several embodiments of the invention are for illustration only, and that various changes in design, structure and arrangement may be made therein without departing from the spirit and scope of the appended claims.
I. In a high energy sonic well drill adapted for attachment to a drill string and having an elastically compliant vertical column of heavy cross section, a periodic force generating oscillator coupled to said column for exerting a vertically directed alternating force thereon at a longitudinal resonant frequency of the column to generate a longitudinal standing wave in the column, with a velocity antinode at each end of the column and a stress antinode at an intermediate region thereof, and a bit connected to the lower end of the column, the combination therewith of improvements for drilling without substantial vibration of the drill string and for suppression of parasitic lateral vibration of said column derived from said longitudinal standing wave therein comprising an elongated jacket structure attached at its upper end to the drill string and concentrically surrounding and extending downwardly along an upper section of said column at a predetermined and fixed slight clearance therefrom which is less than the half-amplitude of parasitic lateral vibration tending to be set up in said column, whereby to effect lateral collision between the laterally vibrating column and the jacket structure, and means connecting said jacket structure to said column at a distance downwardly from the velocity antinode at the upper end of the column equal to at least an eighth Wave length distance along the column for the longitudinal standing wave therein, said bit being of larger diameter than said jacket structure so as to provide for accommodation of the jacket structure in the well bore.
2. The subject matter of claim 1, wherein said jacket structure is connected to said column in the region of a '11 stress antinode of the longitudinal standing Wave therein.
3. The subject matter of claim 1, wherein said bit is of just slightly larger diameter than the jacket structure, whereby the jacket structure is laterally guided and supported by the walls of the well bore. 5
References Cited in the file of this patent UNITED STATES PATENTS 886,704 King May 5, 1908 10 12 Wright Aug. 24, Musschoet Sept. 27, Bodine May 22, Lattig 'Jan. 1, De Jarnett Nov. 26, Smith Apr. 15, Mathewson et a1. Sept. 8, Bodine Sept. 8, Libby Sept. 22, Bodine et aul Sept. 20,